VPS Cleanup

On a box where several agent sessions run at once, "stale-looking" is not "unused": a /tmp worktree can back someone's open PR, a <none> image can back a running container, a cache dir can be held open by a live process. Work in tiers: survey read-only, clear regenerable caches, then ask the user once, batched before each approval tier. Anything uncertain goes on the keep list with its reason.

0. Survey (read-only, delete nothing)

1. Baseline: df -h /, docker system df, docker buildx du. Trust buildx du for build cache: docker system df can report most of it as non-reclaimable (shared vs private records) while buildx du shows all of it reclaimable.
2. Size directories in the background: du across large file counts (node_modules, pnpm stores) runs for minutes and hits tool timeouts in the foreground.